Use of a stabilizer combination in the production of films of polyvinyl chloride by the calendering process

ABSTRACT

The invention concerns the use of a stabilizer combination for polyvinylchloride-based moulding compounds. The stabilizer combination contains (a) at least one solid inorganic component in amounts ranging from 0.3 to 3 parts by weight, relative to 100 parts by weight of polyvinylchloride, selected from sodium aluminosilicates, hydrotalcites and calcium-aluminium-hydroxy-phosphites, and (b) at least one solid or liquid zinc salt in amounts corresponding to a zinc to component (a) ratio of from 0.02 to 0.25 to 1, selected from zinc salts of monocarboxylic acids, substituted or unsubstituted benzoic acid and dicarboxylic acids. This stabilizer combination is used in the production of half-hard and soft polyvinylchloride foils by the calendering process in order to prevent a build-up of coating on the rollers used in this process.

FIELD OF THE INVENTION

This invention relates to the use of a stabilizer combination formolding compounds based on polyvinyl chloride (PVC) in the production ofsemirigid and flexible films of polyvinyl chloride by the calenderingprocess for avoiding plate-out on the rolls used. In the context of theinvention, the expression "molding compounds based on polyvinylchloride" is understood to include both molding compounds based onconventional homopolymers or copolymers of vinyl chloride and thosebased on blends of polyvinyl chloride compounds with other polymers. Theexpression also encompasses suspension, bulk and emulsion polyvinylchloride.

BACKGROUND OF THE INVENTION

Hitherto, liquid barium/cadmium stabilizers have normally been used inthe thermoplastic processing of semirigid PVC and flexible PVC to formfilms by the calendering process. However, since toxic heavy metals,such as cadmium, are no longer acceptable today for reasons of factoryhygiene and ecology, stabilizer systems based on liquid barium/zincstabilizers have been increasingly used for the application mentioned.However, since the heavy metal, barium, also shows relatively hightoxicity, there is a general trend in practice to replace thesebarium/zinc stabilizers also by physiologically safe calcium/zincstabilizers.

In the calendering of flexible and semirigid PVC, the stabilizer systemused has to meet stringent requirements. On the one hand, good earlycolors coupled with adequate color hold are required; on the other hand,the calendering process and the film properties often additionallyrequired, such as good weathering resistance, not only have to guaranteeexcellent long-term stabilities, they are also expected to ensureproblem-free regenerate processing. In addition, the stabilizer systemsused should also reduce the tendency towards blocking and, hence, shouldenable the film to be removed more easily from the hot calender rollsand should have such rheological properties that the films are free fromflow structures and do not have any defects. All these requirements haveto be viewed in particular against the background of the highcalendering speeds now typically encountered in practice. Anothercrucial requirement which stabilizers used for this purpose are expectedto satisfy is the following: they should not cause any plate-out oncalender rolls, take-off and cooling rolls or on any following embossingand laminating units.

The liquid Ba/Cd and Ba/Zn stabilizers normally used for the productionof semirigid and flexible PVC films adequately satisfy the requirementsdiscussed above. Although Ca/Zn stabilizers do not cause any plate-outon calender rolls, they often show only inadequate thermal stability andlong-term stability. By contrast, hitherto known solid Ca/Zn stabilizersshow the required long-term stability coupled with good early colors andcolor hold providing relatively large quantities of metal soaps areused. Unfortunately, stabilizers such as these cause such seriousplate-out on calender rolls that they cannot be used in practice for theproduction of calendered films of flexible or semirigid PVC.

On the subject of known stabilizer systems containing calcium and/orzinc salts of fatty acids, reference is made for example to thefollowing publications:

DE-A-31 13 442 relates to stabilized PVC molding compounds containing astabilizer combination based on alkali metal, alkaline earth metaland/or zinc soaps, co-stabilizers, fine-particle crystallinewater-containing alkali metal alumosilicates, lubricants and,optionally, other typical additives. Crucially, these stabilizercombinations--in addition to an alkali metal alumosilicate--must alsocontain a co-stabilizer selected from β-diketones, α-ketoenol esters,α-acyl lactones, substituted 1,4-dihydropyridine dicarboxylic acids andoptionally substituted pyrroles. In one preferred embodiment, calciumsoaps are used in conjunction with zinc soaps.

EP-A-0 027 588 describes stabilizer combinations for PVC moldingcompounds which contain the following components: fine-particlecrystalline water-containing sodium alumosilicates, calcium salts offatty acids, zinc salts of fatty acids, partial esters of fatty acidsand polyols and thioglycolic acid esters of polyols and/or monohydricalcohols.

Finally, DE-A-41 34 325 relates to a process for stabilizing polymersbased on chlorine-containing olefins using a stabilizer mixturecontaining the following components: calcium complexes of 1,3-diketones,zinc and optionally calcium salts, β-diketones, hydrotalcites, sodiumalumosilicates and/or calcium/aluminium hydroxyphosphites and alsopolyols and/or hydroxyfunctional isocyanurates.

However, it has been found in practice that, where the stabilizercombinations disclosed in the prior art are used for the production ofsemirigid and flexible films of PVC by the calendering process, not allthe requirements mentioned above are adequately satisfied. Inparticular, the formulations in question cause plate-out on calenderrolls.

By contrast, the problem addressed by the present invention was toprovide a stabilizer combination for the production of semirigid andflexible films of PVC which would meet the stringent thermal stabilityrequirements of the calendering process (good initial color, color holdand long-term stability) and which, at the same time, would not causeany plate-out on the calender rolls or following machinery, such astake-off, laminating and embossing units.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to the use of a stabilizercombination for molding compounds based on polyvinyl chloride whichcontains

a) at least one solid inorganic component in quantities of 0.3 to 3parts by weight per 100 parts by weight of polyvinyl chloride selectedfrom:

a1) synthetic, crystalline, fine-particle sodium alumosilicatescontaining 7 to 25% by weight of bound water and corresponding--in thewater-free form--to formula (I):

    0.7 to 1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3 to 5 SiO.sub.2  (I)

a2) optionally surface-modified hydrotalcites corresponding to formula(II):

    Mg.sub.1-x Al.sub.x (OH).sub.2 A.sub.x/n.sup.n-.mH.sub.2 O (II)

in which 0<x<0.5, m is a positive number and A^(n-) is an anion with avalency of 1, 2 or 3,

a3) basic calcium/aluminium hydroxyphosphites corresponding to formula(III):

    Ca.sub.z Al.sub.2 (OH).sub.2(z+2) HPO.sub.3.pH.sub.2 O     (III)

in which z is a number of 2 to 8 and p is a number of 0 to 12,

b) at least one solid or liquid zinc salt selected from

b1) zinc salts of saturated or unsaturated, linear or branchedmonocarboxylic acids containing 6 to 36 carbon atoms,

b2) zinc salts of unsubstituted or C₁₋₄ -alkyl-substituted benzoic acid,

b3) zinc salts of saturated or unsaturated dicarboxylic acids containing6 to 10 carbon atoms, in quantities corresponding to a ratio of zinc tocomponent (a) of 0.02 to 0.25:1, in the production of semirigid andflexible films of polyvinyl chloride by the calendering process foravoiding plate-out on the rolls used.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that, in the calendering of semirigid and flexible PVCfilms, the relatively large quantities of calcium soaps normally used inconventional Ca/Zn stabilizer systems are responsible for plate-out oncalender and take-off rolls and on laminating units. Surprisingly, ithas also been found that the calcium soaps in question can be replacedby the solid inorganic components (a) mentioned above without anydeterioration in the required thermal stability values. Accordingly, thefunction of these calcium soaps as a long-term stabilizer is taken overby the solid inorganic components (a), the adverse effects otherwiseobserved in the form of plate-out on the rolls being completelysuppressed.

As mentioned at the beginning, the present invention relates to moldingcompounds based on polyvinyl chloride (PVC), this expressionencompassing conventional homopolymers or copolymers of vinyl chlorideand also blends of such polyvinyl chloride compounds with otherpolymers. Corresponding polymers may have been produced in any way, forexample by suspension, emulsion or block polymerization. They may have Kvalues of, for example, about 65 to 80. The polyvinyl chloride used forthe purposes of the invention preferably contains plasticizers inquantities of 10 to 100 parts by weight and, more particularly, inquantities of 30 to 60 parts by weight to 100 parts by weight ofpolyvinyl chloride. The so-called "semirigid" PVC films containplasticizers in quantities of, for example, 10 to 25 parts by weightwhile the so-called "flexible" PVC films contain plasticizers inquantities of 25 to 100 parts by weight to 100 parts by weight ofpolyvinyl chloride. The plasticizers used may be any of the conventionaltypes described in the prior art literature, cf. for example H. Kopsch,"Kalandertechnik" , Carl Hanser Verlag (1978), pages 133 to 136.

As mentioned above, the solid inorganic component (a) of the stabilizercombination to be used in accordance with the invention may be selectedfrom sodium alumosilicates, hydrotalcites and basic calcium/aluminiumhydroxyphosphites. The following observations apply in this regard:

In their water-free form, the synthetic, crystalline fine-particlesodium alumosilicates containing 7 to 25% by weight of bound watermentioned under (a1) correspond to formula (I):

    0.7 to 1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3 to 5 SiO.sub.2  (I)

The synthetic crystalline sodium alumosilicates thus defined arezeolites known per se. The general formula encompasses both zeolites oftype A and those of type P, i.e. zeolite types which differ onlyslightly in their chemical composition, but very considerably in regardto their structure and properties. Apart from their chemicalcomposition, X-ray diffractograms are normally used to identify suchzeolite types.

In their water-free form, zeolites of the A type may be characterized bythe following formula:

    0.7 to 1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3 to 2.4 SiO.sub.2

The zeolites A to be used in accordance with the present inventioncontain 13 to 25% by weight of bound water. Zeolites A with a watercontent of 18 to 25% by weight are preferably used for the purposes ofthe present invention. In addition, zeolites A with a particle size of0.1 to 20μ are preferably used as component (a1). Corresponding zeolitesA can be produced by known methods as described, for example, in DE-B-2412 837. Reference is also made to the disclosures of the followingdocuments: DE-A-41 34 325, EP-A-0 027 588, DE-A-29 41 596 and DE-A-31 13442.

Zeolite P has many structurally different variants which differ aboveall in the symmetry of the crystal lattice. P zeolites of the P_(c) type(cubic form) which--in their water-free form--may be characterized bythe following formula:

    0.7 to 1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.8 to 3 SiO.sub.2

are preferably used for the purposes of the present invention. Theygenerally contain from 7 to 25% by weight of bound water. Information onthe production of these zeolites can be found, for example, in thedisclosures of DE-A-39 23 462 and WO 94/03573.

Component (a2) may be selected from optionally surface-modifiedhydrotalcites corresponding to formula (II):

    Mg.sub.1-x Al.sub.x (OH).sub.2 A.sub.x/n.sup.n-.mH.sub.2 O (II)

in which 0<x<0.5, m is a positive number and A^(n-) is an anion with avalency of 1, 2 or 3.

Hydrotalcites such as these are also known compounds which may beproduced by various methods. Hydrotalcites suitable for use inaccordance with the invention may be produced, for example, by theprocesses described in U.S. Pat. Nos. 3,539,306, 3,650,704, 3,875,525and DE-C-15 92 126. Hydrotalcites corresponding to general formula (II),in which A stands for the carbonate anion, are preferred. Particularlypreferred hydrotalcites are those with a specific BET surface of no morethan 30 m² /g and especially those which are commercially availableunder the name of Alcamizer® from Kyowa Chemical Int. which have aspecific BET surface of 8 m² /g (cf. the information pamphlet entitled"Introduction of Alcamizer", Kyowa Chemical Int. Co. Ltd., pages 2 to36, Isuriganecho, Higashi-Ku, Osaka). More information on thehydrotalcites suitable for use in accordance with the invention can befound in the disclosures of the following documents: EP-B-0 063 180 andDE-A-41 34 325.

The basic calcium/aluminium hydroxyphosphites to be used as component(a3) in accordance with the invention correspond to formula (III):

    Ca.sub.z Al.sub.2 (OH).sub.2(z+2) HPO.sub.3.pH.sub.2 O     (III)

in which z is a number of 2 to 8 and p is a number of 0 to 12. Thesebasic calcium/aluminium hydroxyphosphites are also known. Theirproduction is described in DE-C-39 41 902. More information on thisclass of compounds can be found in the disclosure of DE-A41 34 325.

If desired, the hydrotalcites in particular and also thecalcium/aluminium hydroxyphosphites may be surface-modified, for examplewith surface-active substances, such as sodium stearate. The productionof such surface-modified compounds is best carried out in an aqueoussuspension to ensure that the surface-active agent can be absorbed ontothe surface of the solid powder.

According to the present invention, sodium alumosilicates of the zeoliteA type and/or hydrotalcites are preferably used as component (a). Inanother preferred embodiment of the invention, components (a1) and/or(a2) are used individually or in the form of a mixture in quantities of0.3 to 2 parts by weight per 100 parts by weight of polyvinyl chloride.

Solid or liquid zinc salts of

(b1) saturated or unsaturated, linear or branched monocarboxylic acidscontaining 6 to 36 carbon atoms or

(b2) unsubstituted benzoic acid or benzoic acid substituted by C₁₋₄alkyl groups or

(b3) saturated or unsaturated dicarboxylic acids containing 6 to 10carbon atoms

are used as component (b) of the stabilizer combination to be used inaccordance with the invention. According to the invention, these zincsalts may be used both individually and in the form of mixtures.

Corresponding zinc salts are known per se. They are generally producedby precipitation of zinc salts with the corresponding carboxylic acidsmentioned above or directly from zinc oxide and these carboxylic acids.Examples of saturated, linear monocarboxylic acids which may be used inaccordance with the invention include hexanoic acid (caproic acid),heptanoic acid (oenanthic acid), octanoic acid (caprylic acid), nonanoicacid (pelargonic acid), decanoic acid (capric acid), undecanoic acid,dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid(myristic acid), pentadecanoic acid, hexadecanoic acid (palmitic acid),heptadecanoic acid, octadecanoic acid (stearic acid), nonadecanoic acid,eicosanoic acid (arachic acid), heneicosanoic acid, docosanoic acid(behenic acid), tricosanoic acid, tetracosanoic acid (lignoceric acid),pentacosanoic acid, hexacosanoic acid (cerotic acid), octacosanoic acid,triacontanoic acid (melissic acid) and montanic acids. Similarly, thecorresponding unsaturated and corresponding branched monocarboxylicacids may be considered for the zinc salts to be used in accordance withthe invention. An example of the substituted benzoic acids mentioned is,in particular, p-tert.butyl benzoic acid. Basic zinc salts of the(ZnO)_(n) Zn(monocarboxylic acid)₂ type, with n=0.5 to 2, may also beused in accordance with the invention. Basic zinc octoate is mentionedas an example of such a salt. These basic zinc salts may also be usedeither individually and in the form of mixtures with the zinc saltsdefined above. Adipic acid, pimelic acid, suberic acid, azelaic acid,and sebacic acid are mentioned as examples of saturated dicarboxylicacids although the corresponding unsaturated dicarboxylic acids mayagain be used.

In another preferred embodiment of the present invention, zinc salts ofsaturated, linear or branched monocarboxylic acids containing 8 to 18carbon atoms may be used as component (b) in quantities corresponding toa ratio of zinc to component (a) of 0.02 to 0.2:1.

As mentioned above, the stabilizing effect of this stabilizercombination of components (a) and (b) is entirely adequate for thepurposes of the invention in regard to the required thermal stabilityvalues. In addition, however, it can be of advantage in accordance withthe invention additionally to incorporate lubricants or release agents(c) to improve the rheological properties of the stabilizer combinationto be used in accordance with the invention.

In another preferred embodiment of the present invention, the additionallubricants or release agents (c) used are solid or liquid calcium saltsand/or magnesium salts and/or aluminium salts selected from

(c1) calcium salts of saturated or unsaturated, linear or branchedmonocarboxylic acids containing 6 to 36 carbon atoms in quantities of0.05 to 0.3 part by weight,

(c2) calcium salts of unsubstituted or C₁₋₄ -alkyl-substituted benzoicacid in quantities of 0.05 to 0.3 part by weight,

(c3) calcium salts of saturated or unsaturated dicarboxylic acidscontaining 6 to 10 carbon atoms in quantities of 0.05 to 0.3 part byweight,

(c4) magnesium salts of saturated or unsaturated, linear or branchedmonocarboxylic acids containing 6 to 36 carbon atoms in quantities of0.05 to 0.4 part by weight,

(c5) magnesium salts of saturated or unsaturated dicarboxylic acidscontaining 6 to 10 carbon atoms in quantities of 0.05 to 0.4 part byweight,

(c6) aluminium salts of saturated or unsaturated, linear or branchedmonocarboxylic acids containing 6 to 36 carbon atoms in quantities of0.05 to 0.4 part by weight,

the parts by weight mentioned being based on 100 parts by weight ofpolyvinyl chloride.

It has surprisingly been found that the small quantities of saltsmentioned above produce an improvement in the rheological propertieswithout causing any plate-out on the rolls used in the calenderingprocess. The calcium, magnesium and aluminium salts mentioned above maybe used both individually and in the form of mixtures as additionallubricants or release agents. So far as the carboxylic acids to be usedin each of components (c1) to (c6) mentioned above are concerned,reference is made to the foregoing observations in connection with thezinc salts to be used in accordance with the invention. The carboxylicacids mentioned here may likewise also be part of the calcium, magnesiumand/or aluminium salts to be used in accordance with the invention asadditional lubricants or release agents.

According to the invention, calcium salts of saturated linearmonocarboxylic acids containing 16 to 22 carbon atoms in quantities of0.1 to 0.2 part by weight per 100 parts by weight of polyvinyl chlorideare used as component (c).

In addition, magnesium salts of saturated linear monocarboxylic acidscontaining 16 to 22 carbon atoms in quantities of 0.1 to 0.4 part byweight per 100 parts by weight of polyvinyl chloride are preferably usedas component (c).

In another preferred embodiment of the present invention, the additionallubricants or release agents (c) are selected from the compounds knownfor this purpose from the prior art. According to the invention,compounds of the following types are preferably used as additionallubricants or release agents: homopolymers and/or copolymers of acrylateand/or methacrylate, oxidized polyethylene waxes, free fatty acidscontaining 8 to 22 carbon atoms and branched isomers thereof, forexample stearic acid or even hydroxystearic acid, α-olefins, wax esters,i.e. esters of relatively long-chain monocarboxylic acids andmonoalcohols, primary and secondary saturated and unsaturated higheralcohols preferably containing 16 to 44 carbon atoms in the molecule,ethylenediamine distearate, montanic acid esters of diols, for exampleethanediol, 1,3-butane diol and glycerol, mixtures of such montanic acidesters with non-esterified montanic acids, partial esters of fatty acidscontaining 8 to 22 carbon atoms and polyols containing 2 to 6 carbonatoms and 2 to 6 hydroxyl groups which contain on average at least onefree polyol hydroxyl group per molecule and other compounds as listed,for example, in L. I. Nass, "Encyclopedia of PVC", Marcel Dekker(1976/1977), Vol. II, pages 644 et seq., more particularly page 651. Inaddition, the mixed esters described in DE-C-19 07 768 with hydroxyl oracid values of 0 to 6 of aliphatic, cycloaliphatic or aromaticdicarboxylic acids containing 2 to 22 carbon atoms in the molecule,aliphatic polyols containing 2 to 6 hydroxyl groups in the molecule andaliphatic monocarboxylic acids containing 12 to 30 carbon atoms in themolecule may also be used with advantage. Examples of these mixed estersare mixed esters of maleic acid/pentaerythritol/behenic acid, mixedesters of adipic acid/pentaerythritol/oleic acid and mixed esters ofadipic acid/pentaerythritol/stearic acid. According to the invention,lubricants or release agents such as these may be used both instead ofand in conjunction with the above-mentioned metal salts of calcium,magnesium or aluminium as an additional lubricant or release agentcomponent (c). Depending on the type of compound used, the quantityadded is from 0.05 to 1.5 parts by weight per 100 parts by weight ofpolyvinyl chloride.

The stabilizer combination according to the invention may optionallycontain additional co-stabilizers. Corresponding co-stabilizers are alsoknown from the relevant prior art literature. According to theinvention, the co-stabilizers to be additionally used are preferablyselected from β-diketones, organic phosphites, polyols, epoxidized oils,esters of epoxidized fatty acids with monoalcohols, calcium complexes of1,3-diketones, thioglycolic acid esters of polyols or monohydricalcohols and antioxidants. These co-stabilizers may also be used eitherindividually and in the form of mixtures with one another. So far astheir compositions are concerned, reference is made to the relevantprior art literature. More specifically, the following observations maybe made in this regard:

β-diketones suitable for the purposes of the present invention arecompounds known per se which are described, for example, in DE-B-27 28865 or in DE-B-26 00 516 or in EP-B-0 063 180. Particularly preferredβ-diketones are selected from benzoyl acetone,bis-(4-methylbenzoyl)-methane, stearoyl benzoyl methane, palmitoylbenzoyl methane, dibenzoyl methane, 4-methoxybenzoyl methane, benzoylacetyl octyl methane, dibutanoyl methane, distearoyl methane, acetylacetone and stearoyl acetone. Corresponding β-diketones are alsodisclosed in DE-A-41 34 325 and in DE-A-31 13 442.

Suitable organic phosphites are secondary and/or tertiary esters ofphosphorous acid with hydroxyl compounds selected from alkanolscontaining 8 to 22 carbon atoms, phenol, C₆₋₁₂ -alkyl-substitutedphenols and polyols containing 2 to 6 hydroxyl groups and 2 to 32 carbonatoms. Corresponding organic phosphites are disclosed, for example, inDE-A-41 34 325 and in DE-A-38 11 493. According to the invention,commercially available solid phosphites may also be used asco-stabilizers.

According to the invention, suitable polyols are those containing 2 to32 carbon atoms and 2 to 6 primary hydroxyl groups and/orhydroxyfunctional isocyanurates. According to the invention, the polyolsare preferably selected from ditrimethylol propane, dipentaerythritoland hydroxyfunctional isocyanurates. Hydroxyfunctional isocyanurates arealso known compounds which may be obtained by ring-opening trimerizationof hydroxyfunctional isocyanates. Among these isocyanurates,tris-(2-hydroxyethyl)-isocyanurate is preferably used.

Epoxidized oils suitable for use in accordance with the presentinvention are epoxides of esters of unsaturated linear fatty acids, forexample epoxidized soybean oil, linseed oil, sunflower oil or tall oil,and alkyl epoxystearates.

The calcium complexes of 1,3-diketones to be used in accordance with theinvention are also known. Corresponding calcium complexes of1,3-diketones are disclosed, for example, in DE-C-27 16 389 and DE-A-4134 325. Calcium acetyl acetonate obtainable from 1 mole of calciumhydroxide and 2 moles of acetyl acetone is preferably used for thepurposes of the invention.

Thioglycolic acid esters suitable for the purposes of the invention arethose of polyols containing 2 to 6 carbon atoms and 2 to 6 hydroxylgroups and/or those of monohydric alcohols containing 8 to 22 carbonatoms. Corresponding thioglycolic acid esters are disclosed, forexample, in EP-A-0 027 588.

Antioxidants suitable for the purposes of the invention are thecompounds known from the prior art, for example 2,6-di-t-butyl-p-cresol,2,5-di-t-butyl hydroquinone,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, diphenylolpropane, 2,5-bis-(1,1-dimethylpropyl)-hydroquinone,1,1,3-tris-(5-t-butyl-4-hydroxy-2-methylphenyl)-butane, and ultravioletabsorbers, such as 2-hydroxy4-octoxybenzophenone andethyl-2-cyano-3,3-diphenyl acrylate.

The stabilizer combination according to the invention and thecomponents, if any, additionally used, as defined in detail in theforegoing, are incorporated in the PVC compounds by mixing, for exampleusing plowshare mixers, high-speed mixers, co-kneaders, pelletizers,mixing rolls, extruders or intensive mixers.

EXAMPLES

Description of the Test Procedures

The stability of the PVC molding compound was assessed from the staticthermal stability of strips. To this end, PVC molding compoundscontaining stabilizer combination were processed on laboratory rolls toform strips. The strips size-reduced to test specimens were then exposedto a temperature of 190° C. in a drying cabinet with revolving trays(Heraeus 6060). Samples were taker at 15-minute intervals and inspectedfor changes in color, a black coloration indicating the end ofstability.

Plate-out was evaluated as follows on computer-controlled measuringrolls (450 mm roll width×252 mm roll diameter): a strip was first formedon the front roll by introducing the mixture and was mixed by hand for 3minutes. The surface temperatures of the rolls were 185° C. (front) and175° C. (rear). After the mixture had been homogenized on the rolls, anautomatic running program was started as follows: by changing thefriction (40%), the strip was transferred from the front roll to therear roll. Plate-out on the chromium-plated roll was then visuallyevaluated at a rotational speed of 10 r.p.m. and with a nip of 0.35 mm.The chromium-plated, mirror-finish rolls enable plate-out to beprecisely evaluated. In another step, it was evaluated whether the stripwas difficult or easy to remove from the roll.

Composition of the PVC Molding Compounds

100 Parts by weight of suspension PVC with a K value of 71 (Solvic® 271GC) was mixed with the compounds listed in Table 1 in the quantitiesindicated (quantities in parts by weight per 100 parts by weight of PVC;phr). Examples 1 and 2 are Comparison Examples.

The terms and abbreviations used in Table 1 have the following meanings:

DiDP plasticizer: phthalic acid diisodecyl ester stabilized with 0.3% byweight of bisphenol A

ESO: epoxidized soybean oil

DPDP: diphenyl isodecyl phosphite

Multicomponent ester: ester mixture of alcohols containing 2 to 6hydroxyl groups with aliphatic monocarboxylic acids containing 12 to 30carbon atoms and aliphatic dicarboxylic acids containing 2 to 22 carbonatoms according to DE-C-19 07 768

BaZn stabilizer: commercial liquid BaZn stabilizer

Zeolite: type A zeolite containing 20% H₂ O according to EP-A-0 027 588

Hydrotalcite: commercial hydrotalcite

CHAP: calcium aluminium hydroxyphosphite

Patent Examples

1 Reference BaZn stabilizer

2 Stabilizer system based on solid CaZn soaps

3 Zeolite/Zn soap (Zn octoate)

4 Hydrotalcite/Zn soap (Zn stearate)

5 CaAl hydroxyphosphite/Zn soap (Zn stearate)

6 Patent Example 1 plus rheology component stearic acid

7 Example 3 plus rheology component liquid multicomponent ester

8 Example 3 plus rheology component Ca stearate/stearic acid

9 Example 3 plus rheology component Mg stearate

10 Example 3 plus rheology component Al stearate

                                      TABLE 1                                     __________________________________________________________________________    Example        1   2    3   4   5   6   7   8   9   10                        __________________________________________________________________________    S-PVC, K value 71                                                                            100 100  100 100 100 100 100 100 100 100                         DiDP plasticizer 60 60 60 60 60 60 60 60 60 60                                ESO 3 3 3 3 3 3 3 3 3 3                                                       Org. phosphite DPDP -- 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8                    Ca stearate -- 0.8 -- -- -- -- -- 0.1 -- --                                   Mg stearate -- -- -- -- -- -- -- -- 0.1 --                                    Al stearate -- -- -- -- -- -- -- -- -- 0.1                                    Stearic acid -- -- -- -- -- 0.2 -- 0.2 -- --                                  Liquid multicomponent ester -- -- -- -- -- -- 0.2 -- -- --                    BaZn stabilizer 2.5 -- -- -- -- -- -- -- -- --                                Zeolite -- -- 1 -- -- 1 1 1 1 1                                               Hydrotalcite -- -- -- 1 -- -- -- -- -- --                                     CHAP -- -- -- -- 1 -- -- -- -- --                                             Zn octoate -- -- 0.5 --  0.5 0.5 0.5 0.5 0.5                                  Zn stearate -- 0.25 -- 0.25 0.25 -- -- -- -- --                               Stat. thermal stability                                                       at 190° C. in the drying cabinet:                                    Initial color  ← Colorless →                                      Early color hold (mins.)                                                                     60  45-60                                                                              60  45  60  60  60  60  60  60                          End of stability (mins.) 105 90 105 90 90 105 105 105 105 105                 Plate-out on the measuring rolls:                                             Yes  x.sup.1                                                                  No x.sup.1  x.sup.2 x.sup.2 x.sup.2 x.sup.1 x.sup.1 x.sup.1 x.sup.1                                                             x.sup.1                   __________________________________________________________________________     .sup.1 Strip shows slight tendency to adhere to the roll on removal           .sup.2 Strip shows greater tendency to adhere to the roll on removal     

What is claimed is:
 1. A process for stabilizing a polyvinylchloride-containing composition used in the production of semi-rigid andflexible films, said process comprising:(i) providing a polyvinylchloride-containing composition; (ii) providing a stabilizer compositioncomprising:(a) at least one inorganic component in an amount of fromabout 0.03 to about 3 parts by weight per 100 parts by weight ofpolyvinyl chloride, wherein the at least one inorganic component isselected from the group consisting of:(a1) synthetic, crystalline,fine-particle sodium aluminosilicates containing from about 7 to about25% by weight of bound water, wherein the sodium aluminosilicates, inwater-free form, correspond to the general formula (I):

    0.7-1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3-5 SiO.sub.2        (I)

(a2) hydrotalcites of the general formula (II):

    Mg.sub.1-x Al.sub.x (OH).sub.2 A.sub.x/n.sup.n-.mH.sub.2 O (II)

wherein 0<x<0.5, m is a positive number and A^(n-) represents an anionhaving a valency of from 1 to 3; (a3) basic calcium/aluminumhydroxyphosphites of the general formula (III):

    Ca.sub.z Al.sub.2 (OH).sub.2(z+2) HPO.sub.3.pH.sub.2 O     (III)

wherein z represents a number of from 2 to 8 and p represents a numberof from 0 to 12; (b) at least one zinc salt in a weight ratio of zinc tocomponent (a) of from about 0.02:1 to about 0.25:1, wherein the at leastone zinc salt is selected from the group consisting of zinc salts ofmonocarboxylic acids having from about 6 to about 36 carbon atoms, zincsalts of dicarboxylic acids having from about 6 to about 10 carbonatoms, zinc salts of benzoic acid, and zinc salts of C₁₋₄ -substitutedbenzoic acid; and (c) at least one component selected from (c1) calciumsalts of saturated linear monocarboxylic acids having from 16 to 22carbon atoms in an amount of 0.1 to 0.2 parts by weight per 100 parts byweight of polyvinyl chloride, and (c2) magnesium salts of saturatedlinear monocarboxylic acids having from 16 to 22 carbon atoms in anamount of 0.1 to 0.4 parts by weight per 100 parts by weight ofpolyvinyl chloride; and (iii) combining the polyvinylchloride-containing composition and the stabilizer composition prior tousing the polyvinyl chloride-containing composition in the production ofsemi-rigid and flexible films.
 2. The process according to claim 1,wherein the polyvinyl chloride-containing composition further comprisesa plasticizer in an amount of from 10 to 100 parts by weight per 100parts by weight of polyvinyl chloride.
 3. The process according to claim1, wherein the polyvinyl chloride-containing composition furthercomprises a plasticizer in an amount of from 30 to 60 parts by weightper 100 parts by weight of polyvinyl chloride.
 4. The process accordingto claim 1, wherein the at least one inorganic component is selectedfrom the group consisting of zeolite A sodium aluminosilicates andhydrotalcites of the general formula (II), wherein the at least oneinorganic component is present in an amount of from about 0.3 to about 2parts by weight per 100 parts by weight of polyvinyl chloride.
 5. Theprocess according to claim 1, wherein the at least one zinc saltcomprises a saturated monocarboxylic acid having from 8 to 18 carbonatoms, and wherein the at least one zinc salt is present in a weightratio of zinc to component (a) of from about 0.02:1 to about 0.2:1. 6.The process according to claim 1, wherein the at least one inorganiccomponent is selected from the group consisting of zeolite A sodiumaluminosilicates of the general formula (IV):

    0.7-1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3-2.4 SiO.sub.2      (IV)

containing from about 18 to about 25% by weight of bound water andhaving a particle size of from 0.1 to 20 μm, and hydrotalcites of thegeneral formula (II) wherein A^(n-) represents a carbonate anion and thehydrotalcite has a specific BET surface value less than or equal to 30m² /g, wherein the at least one inorganic component is present in anamount of from about 0.3 to about 2 parts by weight per 100 parts byweight of polyvinyl chloride.
 7. The process according to claim 6,wherein the at least one zinc salt comprises a saturated monocarboxylicacid having from 8 to 18 carbon atoms, and wherein the at least one zincsalt is present in a weight ratio of zinc to component (a) of from about0.02:1 to about 0.2:1.
 8. The process according to claim 1, wherein theat least one component (c) is selected from the group consisting ofcalcium stearate and magnesium stearate.
 9. The process according toclaim 6, wherein the at least one component (c) is selected from thegroup consisting of calcium stearate and magnesium stearate.
 10. Theprocess according to claim 7, wherein the at least one component (c) isselected from the group consisting of calcium stearate and magnesiumstearate.
 11. A stabilized polyvinyl chloride-containing compoundproduced by the process according to claim
 1. 12. A stabilized polyvinylchloride composition comprising:(i) a polyvinyl chloride-containingcomposition; and (ii) a stabilizer composition, wherein the stabilizercomposition comprises:(a) at least one inorganic component in an amountof from about 0.03 to about 3 parts by weight per 100 parts by weight ofpolyvinyl chloride, wherein the at least one inorganic component isselected from the group consisting of:(a1) synthetic, crystalline,fine-particle sodium aluminosilicates containing from about 7 to about25% by weight of bound water, wherein the sodium aluminosilicates, inwater-free form, correspond to the general formula (I):

    0.7-1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3-5 SiO.sub.2        (I)

(a2) hydrotalcites of the general formula (II):

    Mg.sub.1-x Al.sub.x (OH).sub.2 A.sub.x/n.sup.n-.mH.sub.2 O (II)

wherein 0<x<0.5, m is a positive number and A^(n-) represents an anionhaving a valency of from 1 to 3; (a3) basic calcium/aluminumhydroxyphosphites of the general formula (III):

    Ca.sub.z Al.sub.2 (OH).sub.2(z+2) HPO.sub.3.pH.sub.2 O     (III)

wherein z represents a number of from 2 to 8 and p represents a numberof from 0 to 12; (b) at least one zinc salt in a weight ratio of zinc tocomponent (a) of from about 0.02:1 to about 0.25:1, wherein the at leastone zinc salt is selected from the group consisting of zinc salts ofmonocarboxylic acids having from about 6 to about 36 carbon atoms, zincsalts of dicarboxylic acids having from about 6 to about 10 carbonatoms, zinc salts of benzoic acid, and zinc salts of C₁₋₄ -substitutedbenzoic acid; and (c) at least one component selected from (c1) calciumsalts of saturated linear monocarboxylic acids having from 16 to 22carbon atoms in an amount of 0.1 to 0.2 parts by weight per 100 parts byweight of polyvinyl chloride, and (c2) magnesium salts of saturatedlinear monocarboxylic acids having from 16 to 22 carbon atoms in anamount of 0.1 to 0.4 parts by weight per 100 parts by weight ofpolyvinyl chloride.
 13. The composition according to claim 12, whereinthe polyvinyl chloride-containing composition further comprises aplasticizer in an amount of from 10 to 100 parts by weight per 100 partsby weight of polyvinyl chloride.
 14. The composition according to claim12, wherein the polyvinyl chloride-containing composition furthercomprises a plasticizer in an amount of from 30 to 60 parts by weightper 100 parts by weight of polyvinyl chloride.
 15. The compositionaccording to claim 12, wherein the at least one inorganic component isselected from the group consisting of zeolite A sodium aluminosilicatesand hydrotalcites of the general formula (II), wherein the at least oneinorganic component is present in an amount of from about 0.3 to about 2parts by weight per 100 parts by weight of polyvinyl chloride.
 16. Thecomposition according to claim 12, wherein the at least one zinc saltcomprises a saturated monocarboxylic acid having from 8 to 18 carbonatoms, and wherein the at least one zinc salt is present in a weightratio of zinc to component (a) of from about 0.02:1 to about 0.2:1. 17.The composition according to claim 12, wherein the at least oneinorganic component is selected from the group consisting of zeolite Asodium aluminosilicates of the general formula (IV):

    0.7-1.1 Na.sub.2 O.Al.sub.2 O.sub.3.1.3-2.4 SiO.sub.2      (IV)

containing from about 18 to about 25% by weight of bound water andhaving a particle size of from 0.1 to 20 μm, and hydrotalcites of thegeneral formula (II) wherein A^(n-) represents a carbonate anion and thehydrotalcite has a specific BET surface value less than or equal to 30m² /g, wherein the at least one inorganic component is present in anamount of from about 0.3 to about 2 parts by weight per 100 parts byweight of polyvinyl chloride.
 18. The composition according to claim 17,wherein the at least one zinc salt comprises a saturated monocarboxylicacid having from 8 to 18 carbon atoms, and wherein the at least one zincsalt is present in a weight ratio of zinc to component (a) of from about0.02:1 to about 0.2:1.
 19. The composition according to claim 12,wherein the at least one component (c) is selected from the groupconsisting of calcium stearate and magnesium stearate.
 20. Thecomposition according to claim 17, wherein the at least one component(c) is selected from the group consisting of calcium stearate andmagnesium stearate.
 21. The composition according to claim 18, whereinthe at least one component (c) is selected from the group consisting ofcalcium stearate and magnesium stearate.